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"""
Ubelt Use Cases
Each use case starts with a modivation and follows with a solution. This makes
these cases perfect for presentations.
"""
def multiple_items_from_a_dictionary():
"""
Spotlight:
ubelt.take
Modivation:
Working with Lists of Dictionaries
Requires:
kwimage
"""
...
"""
When working with data, a common pattern is to iterate through it, and
gather information about the work to be done, so a you can make a final
structured pass through the data.
In python we might do this by initializing an empty list and appending
**dictionary of information**, to the list. (or you might yield
dictionaries of information from a generator instead, either way you have a
flat list).
Some people might use lists of tuples instead of Lists of dictionaries, but
using dictionaries makes it easy to add new information later (and it works
very will with pandas).
"""
import ubelt as ub
import kwimage
kwimage_test_image_names = ['airport', 'amazon', 'astro', 'carl',
'lowcontrast']
rows = []
for test_image in kwimage_test_image_names:
fpath = ub.Path(kwimage.grab_test_image_fpath(test_image))
imdata = kwimage.imread(fpath)
row = {
'mean': imdata.mean(),
'std': imdata.std(),
'sum': imdata.sum(),
'max': imdata.max(),
'min': imdata.min(),
}
rows.append(row)
"""
For each row, you might want to grab multiple specific items from it.
But having a separate assignment on each row wastes a lot of vertical
space.
"""
for row in rows:
mean = row['mean']
std = row['std']
sum = row['sum']
min = row['min']
max = row['max']
"""
You might put them one line explicitly, but that wastes a lot of horizontal
space
"""
for row in rows:
mean, std, sum, min, max = row['mean'], row['std'], row['sum'], row['min'], row['max']
"""
What if we try to be clever? We can use a list comprehension
"""
for row in rows:
mean, std, sum, min, max = [row[k] for k in ['mean', 'std', 'sum', 'min', 'max']]
"""
That's not too bad, but we can do better
"""
for row in rows:
mean, std, sum, min, max = ub.take(row, ['mean', 'std', 'sum', 'min', 'max'])
"""
And now even better:
"""
for row in map(ub.udict, rows):
mean, std, sum, min, max = row.take(['mean', 'std', 'sum', 'min', 'max'])
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